After learning that Ashton Kutcher had landed in the hospital trying to follow Steve Jobs ' all-fruit diet , CNN reader Sumday had just one question : `` All I really wanted to know was why this diet was bad ? ''

Jobs first fell for extreme diets during his freshman year of college , according to Walter Isaacson 's biography `` Steve Jobs . '' Jobs and his college friend Daniel Kottke became vegetarians after reading `` Diet for a Small Planet . ''

Then Jobs read `` Mucusless Diet Healing System '' by Arnold Ehret ; Ehret believed in eating nothing but fruits and starchless vegetables like spinach , carrots and cucumbers . Jobs began with two-day fruit fasts , eventually going for a week or more . `` I got into it in my typical nutso way , '' Jobs told Isaacson .

Ehret 's fruitarian diet , also called the Eden Garden Diet or Ehretism , is often used as a type of cleanse , according to LiveStrong.com . Designed to detoxify the system , it can do more long-term harm than good .

When you only eat fruit , you 're excluding a lot of valuable nutrients from your diet , says Marisa Moore , registered dietician and spokeswoman for the Academy of Nutrition and Dietetics .

`` Protein is one of the main ones that comes to mind , '' she says . '' -LRB- Without protein -RRB- you lose body weight . Protein acts like a building block for your muscles and skin and organs . ''

The same goes for fats , Moore says . Although they often get demonized , fats play an important role in our hormone levels and brain function .

Kutcher told reporters at the Sundance Film Festival that he ended up in the hospital with pancreas levels that were `` completely out of whack . ''

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Fruit contains a lot of natural sugar , which needs to be controlled by insulin in the body , Moore says . It 's the pancreas ' job to release that insulin ; Kutcher 's pancreas may have been overworked if his body was receiving an overload of sugar .

Many readers wondered if an all-fruit diet could have led to Jobs ' pancreatic cancer , which led to his death in October 2011 . Scientists do n't know what causes pancreatic cancer , according to the American Cancer Society . Certain inherited DNA mutations might play a role , as well as chemicals in our environment or diet .

Even if you do n't overwork your pancreas , you 're probably not eating enough calories on an all-fruit diet , Moore says . That puts the body into starvation mode , which can result in serious medical conditions like osteoporosis , severe dehydration and even heart failure , according to the National Eating Disorders Association .

Here 's the bottom line : Fruit is natural . It 's nutritious . The government recommends eating 1 to 2 cups of it a day . Just do n't go all `` nutso '' on it .

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Ashton Kutcher is playing Steve Jobs in Joshua Michael Stern 's biopic `` Jobs ''

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Kutcher ended up in the hospital after trying to follow Jobs ' all-fruit diet

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All-fruit meals can exclude valuable nutrients from your diet , nutritionist says